Insights from the trends of omalizumab and mepolizumab utilization in patients with asthma: A population-based cohort study using the National Database in Japan

Background: Biologics are increasingly being used in patients with severe uncontrolled asthma. However, the trends in their use for treating severe asthma in Japan remain unclear. Methods: The number of patients with asthma prescribed omalizumab or mepolizumab between April 2017 and March 2018 was estimated according to sex, age, and geographical region using data from the National Database of Health Insurance Claims and Specific Health Checkups of Japan. Results: Overall, 5,014, 3,449 and 7,977 patients were prescribed omalizumab, mepolizumab, or either combination, respectively. The total number of patients prescribed biologics displayed a bimodal distribution with peaks in their early teens and seventies. Biologics were most commonly used by male and female patients in their seventies. Prescription was 1.24 times higher in males than in females up to the teenage years, whereas it was 1.95 times higher in females than in males from their twenties onwards. Omalizumab was prescribed 1.45 times more frequently than mepolizumab, especially in pediatric patients, and was prescribed 1.96 times more often to female patients than to male patients. Regional differences were observed in the proportion of patients prescribed biologics. Correlation analysis suggested a weak relationship (r = 0.3226, p = 0.0270) between the proportion of patients prescribed biologics and board-certified allergists according to the geographic region. Conclusions: In Japan, biologics are prescribed more often to older patients with severe asthma compared to those in other countries. Thus, eliminating the regional disparities in asthma treatment by specialists is necessary to provide appropriate medical care to patients with severe asthma.